This is on a generic x86_64 LibreELEC Nightly 4 september after today's upgrade to 12.80.7.19
LibreELEC:~ # grep version= .kodi/addons/tools.flatpak/addon.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<addon id="tools.flatpak" name="Flatpak" version="12.80.7.19" provider-name="Team LibreELEC">
<requires><import addon="xbmc.python" version="3.0.0"/>
<import addon="tools.gnupg" version="0.0.0" />
<import addon="tools.externalhelper" version="0.0.0" />
LibreELEC:~ # flatpak
flatpak: error while loading shared libraries: libarchive.so.13: cannot open shared object file: No such file or directory
LibreELEC:~ # which flatpak
/storage/.kodi/addons/tools.flatpak/bin/flatpak